Sarah Grace, a twin, was born with Down syndrome, a common genetic disorder that affects about 400,000 Americans. Up to 70% of children with Down syndrome suffer from hearing problems, and Ashley Davis worried Sarah Grace's inability to hear would keep her daughter from learning to speak.

"And kids with Down syndrome are already at a disadvantage, as far as speech is concerned,” says Ashley. “They already have speech delays. So to add hearing loss to that, the odds are stacked against her."

So, Tonya Nussbaum, a Children's Healthcare of Atlanta audiologist, is fitting Sarah Grace with her second pair of ear moldings. Sarah Grace lost one of the first two moldings, which is common with young children.

Nussbaum says the toddler suffers from “conductive” hearing loss, because of structural problems with her ear.

"The hearing nerve is working fine,” she says. “The sound just can't get through there because of infections and fluid."

Sarah Grace is already extremely outgoing. So Nussbaum helping her hear better, will help her interact better with the people around her, like her twin Hannah.

"Sometimes people with hearing loss just appear quiet or withdrawn,” says Nussbaum. “And it's not necessarily that they are quiet; they're just not catching the conversation or different things in the environment. It's difficult to respond to them when they can't hear them."

Sarah Grace has only had her hearing aids for about two months, but her dad Harmon Davis is already seeing big changes.

“We get to see her respond a lot more, she's hearing a lot more words,” Harmon Davis says. “Which is great because our biggest problem is communication with her."

Ashley Davis says the change in Sarah Grace is “amazing.”

"You put in her hearing aids, and it used to be she would be running away from you as fast as she could down the hall,” Ashley says. “Now, you say, ‘Sara!’ And she'll turn around, and she'll look at you, and she will actually stop and come back to you now. Hugely different."

Nussbaum says she loves seeing kids like Sarah Grace respond to the world they've been missing.

'That's the best part of my day,” she says. “Absolutely the highlight."